1. Field of the Invention:
This invention relates to fiber-optic communication systems. More specifically, this invention relates to optical amplification arrangements for fiber-optic communication systems.
While the present invention is described herein with reference to a particular embodiment, it is understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional embodiments within the scope thereof.
2. Description of the Related Art:
In certain remote-guidance systems, communication with a guided vehicle is facilitated by an optical fiber link between the vehicle with a control station. The optical fiber is typically wound around a bobbin, or secured by other means capable of dispensing the fiber as the vehicle travels downrange. An optical carrier of a first wavelength is used to transport commands from the control station to the vehicle, while data from the vehicle is impressed upon an optical carrier of a second wavelength and carried by the fiber to the control station. Hence, bidirectional communication is effectuated in conventional fiber-optic systems by using optical energy at a pair of wavelengths to carry information in opposing directions.
Unfortunately, signal loss induced by the connecting fiber is typically minimized only at relatively long optical wavelengths. Since the optical carriers propagating in opposite directions along the link must generally be separated by a sufficient wavelength spacing to prevent inter-channel interference (cross-talk), it is generally not possible to choose the wavelength of both carriers to be within the relatively narrow wavelength spectrum of minimal signal loss. Accordingly, the signal transmission range of conventional dual-wavelength bidirectional optical fiber communication links is less than would be possible for a fiber link operative within a wavelength spectrum of minimal signal loss.
Fiber-induced signal loss generally necessitates intermediate amplification in long range systems. However, in conventional dual wavelength systems complex and expensive optical repeaters are used for signal amplification. Optical repeaters operate by first converting the signals carried by the light energy back to the electrical domain. Next, these extricated electrical signals are superimposed upon a separately generated optical carrier. In addition, optical repeaters complicate system design as these circuits often need to be included at multiple locations in very long-range fiber-optic links.
It follows that a need in the art exists for an optical amplifier suitable for use in a long-range fiber-optic communication link, wherein the amplifier is operative over an optical spectrum of minimal fiber-induced signal loss.